https://www.youtube.com/watch?v=o8Fn9BgqoQM

first time :
	npm install --save express
	npm install --save socket.io
	sudo npm install -g nodemon

next time :
	npm install

anytime :
	nodemon server

- [ ] don't send message to oneself
- [ ] create a room
- [ ] automatically add someone to a room
- [ ] being able to accept or refuse to be added to a room
- [ ] what to do with message not received ?